The printheads of Inkjet printers have a series of nozzles from which individual ink droplets are ejected to deposit on print media to form desired printed images. The nozzles are incorporated in various types of printheads and their proper functioning is critical to the creation of quality images. Thus, any partial or total blockage of even a single nozzle may have a significant impact on a printed image, particularly in the case of a pagewidth printer.
The nozzles are prone to blockage due to their exposure to ever-present paper dust and other particulate matter and due to the tendency of ink to dry in the nozzles during, often very short, idle periods. That is, ink which is awaiting delivery from a nozzle forms a meniscus at the nozzle mouth and, when exposed to (frequently warm, dry) air, the ink solvent is evaporated to leave a nozzle blocking deposit.
Servicing systems are conventionally employed for maintaining the functionality of printheads, such systems providing one or more of the functions of capping, purging and wiping. Capping involves the covering of idle nozzles to preclude exposure of ink to drying air. Purging is normally effected by sucking deposits from the printhead that block or have the potential to block the nozzles. Wiping is performed in conjunction with the capping and/or purging functions and involves gently sweeping a membrane across the face of the printhead.
The majority of conventional inkjet printers, particularly so-called desk top printers, employ reciprocating printheads which, as above mentioned, are driven to traverse across the width of momentarily stationary print media. In these printers, service stations are provided at one side of the printing zone and, on command, the printhead is traversed to the service station where it is docked for such time as servicing is performed and/or the printer is idle. However, inclusion of the service stations increases the total width of the printers and this is recognised as a problem in the context of trends to minimise the size of desk-top printers.
Moreover, the above described servicing system cannot feasibly be employed in relation to pagewidth printers which, as above mentioned, have a stationary printhead that extends across the full width of the printing zone. The printhead has a length that effectively defines the printing zone and it cannot be moved outside of that zone for servicing. Furthermore, a pagewidth printhead has a significantly larger surface area and contains a vastly greater number of nozzles than a reciprocating printhead, especially in the case of a large format printer, all of which dictate an entirely different servicing approach from that which has conventionally been adopted.
Also, in the case of a pagewidth printer it is most desirable that the printhead be not moved relative to its supporting structure, and this gives rise to the following requirements:
1. The servicing system must be moved to the printhead to effect a servicing operation.
2. The servicing system must be moved away from the region of the printhead during a printing operation, to permit passage of print media.
3. The servicing system should desirably be moved into servicing engagement with the printhead in a manner that minimises the risk of damage being done to the printhead nozzles.
Furthermore, capping facilities, whether of the capping mechanism type or the service station type, should advantageously be protected against loss of contained moisture and ingress of contaminating material. That is, it has been recognised that contained moisture should be maintained in the capping facility between capping operations, so as to minimise the risk of nozzle blockage during a capping operation. Similarly, contaminating material should be excluded from the capping facility during intervals between capping operations.